How Do I Navigate Astronomical Catalogues?

Which Catalogues Will You See in Your Go-To Telescope Menus?

So how do catalogues help us? Catalogues make navigating the night sky magnitudes easier than it otherwise would be. Objects within the universe are assigned a catalogue number if they fit the requirement criteria of that catalogue. For example, the bright star Betelgeuse does not have a designation in the ADS catalogue but the double star Albireo does (ADS 12540). Therefore, all an astronomers requires when operating a go-to telescope (after alignment of course) is a catalogue number for the object they wish to observe. Should the telescope’s guiding computer contain the desired catalogue, it will be able to instantly and accurately slew to the DSO.

This raises the question of which catalogues are most likely to be used by amateur astronomers. Catalogues such as the HEASARC catalogue (catalogue of known radio sources) and the XRAY catalogue (catalogue of known x-ray sources) are not useful to amateur astronomers who observe the universe in the visual spectrum. Fortunately for amateur astronomers, all modern go-to telescopes have some of the larger DSO catalogues already programmed into their hardware. These catalogues include:

M – The Messier Catalogue

17^th century astronomer Charles Messier spent most of his professional astronomical career searching for fleeting visitors to the inner solar system, comets. Across his comet hunting career Messier discovered 13 comets and co-discovered one more. However, Messier is not remembered in modern astronomy by his catalogue of comets. He is instead remembered for his contribution to the field of deep sky observation. During many of his comet hunts Messier came across objects which frustrated him, he would observe what he thought to be a comet and return to it at a later date only to find the object had not moved, a good indicator that the object is not a comet. By the end of his career Messier had found 103 DSOs, including open clusters, globular clusters, galaxies, diffuse nebulae and planetary nebulae. The Messier catalogue is a fantastic catalogue for amateur astronomers as all most, if not all, of the objects are visible even with entry level telescopes.

NGC – The New General Catalogue

Originally put together in the 1800s by astronomer John Louis Emil Dreyer, the New General Catalogue is a catalogue of 7,840 deep sky objects. The NGC catalogue contains many galaxies, star clusters and all types of nebulae meaning that most objects in the night sky can be found in the New General Catalogue. Unfortunately for Dreyer, the creation of the catalogue was quite difficult. Due to the sheer amount of objects he included, Dreyer was not able to observe and confirm all of the objects submitted to him. As such, the catalogue contained several erroneous entries upon initial publication, most of which related to position and description of the object. Fortunately for us, astronomers in future years would return to the catalogue and make the necessary updates.

IC – The Index Catalogue

His work not yet done, Dreyer published two updates to his New General Catalogues in 1895 and 1908. These updates became known as the Index Catalogue, and introduced a further 5,386 deep sky objects to the New General Catalogue. IC summarises the newly discovered galaxies, clusters and nebulae which were found between 1888 and 1907. This massive increase in DSO was made possible by the advent of photography.